A nation that never constructed a submerged tunnel tackles the challenge of building the deepest immersed highway on Earth. Everything about the project is super-sized. Each of the tunnel’s mammoth segments is as long as two football pitches and as heavy as an aircraft carrier. Yet all the segments must align within 35 millimeters -- less than a thumb’s width. To compound the challenge, all work has to be timed around the fickle weather of the Pacific. And the tunnel itself must be able to withstand earthquakes and typhoons. To succeed, engineers will have to invent a raft of ingenious solutions.